CrazyHawaiian

I've been troubleshooting an idle/stall issue for a few weeks now and I finally have a possible "culprit" that might explain all the problems/symptoms. I wrote this up over a few days and I wanna post it in hopes some of you guys can help me. Its kinda long so I dont blame you if you dont wanna read it.

Here's how it started.

The beginning - a slight pinging or knocking sound coming from the engine at idle after making some runs at the drift session. Idle was perfect and no stalling. Suspected the valves. Drove home fine.

Portaghee fix - Deciding that the engine was on its last legs and about to require some sort of major internal work, do the cheapest thing that might make it last a little longer for another drift session (chance em). Changed the oil and filter and added Barrs Leaks engine stop knock additive.

Confusion begins - Engine stops making the slight pinging or knocking sound but now begins to idle real rough and stall out after 10-15 seconds of operation. Engine will crank over and start every time. After engine stalls SES light is on solid. Put car in gear and it still idles rough and stalls.

Troubleshooting - Fuel, Air, Spark .. proved out air and fuel first since they were easiest. Disconnected the intake ducts from the filter housing and proped them up providing direct airflow into the MAF, symptoms did not change. Hooked up a psi guage to the fuel rail and put the ignition on, fuel steady ay 44psi ('89 L98 TPI). Start the car and psi drops 3 to 41psi and remains constant as symptoms remain the same. Fuel pressure does not fluctuate at all during the rough idle or stall. Narrowed it down to spark which also includes all the electronics (sensors and such).

Stumped - Pull the error codes on the ECM and getting a constant code 12 forever. This is either the handshake code, or the no signal from distributor code which its supposed to read when the ignition is on but the car is off and you pull codes. So no obvious sensor issues. I decide maybe they're dirty or stuck and putting out low voltage outputs, pull out the plugs to the distributor (plugs down below the cap), the coil, all plug wires on the cap, the TPS and IAC and throughly clean them all with wire brushes and electronics cleaner (carefull not to spray into the sensors themselves). Rehooked everything and double checked all connections were proper. Started it back up and the idle was smoother and not as erratic, but it still stalled after 10-15 sec of running.

Keep going - Decided to individually start unplugging sensors and start the car, forcing the ECM to ignore the sensor and use pre-determined values from the ECM chip. Started with the MAF, unplugged it (should test out bad MAF sensor or relays) but symptoms did not change. Plugged it back in and unplugged the TPS. Now something changed. Car idled real high at 2,000 rpm but did not stall out, and in fact was able to idle for 20 minutes with no issues, no rough idle, no stumbling, just very high idle. Decided it was a faulty TPS. High idle brings out the slight pinging or knocking sound again, not sure what to think. Did not remember to check the ECM and see if it was in open or closed loop (but now I assume it was in open)

Dirty bastards - Drove to the other side of the island to get the TPS only to find it was the wrong type and the place I originally came from had the part I needed. Got my hands on the TPS sensor, installed it, and car idled high at around 1200-1500 rpm but steady idle and no stalls. Very similar to how it acted earlier when the sensor was unplugged and using predetermined values. I decided this was a good sign that the sensor issue was solved, all sensors were plugged in and the car did not stall. Kept in mind that the TPS still needed to be adjusted to the proper .54 volts output and possibly the IAC needed to be cleaned again so not too worried about the high idle. Put the car in gear and it instantly stalls and dies. Try it a few times and it dies every time it gets put in gear. So now it idles high and steady in park but stalls instantly when put in gear.

Keep going - I had a MSD dist cap and rotor ready to go so I decided to swap em in and see what happens. At this point I assume all sensors are good and its either a spark issue of some sort or a vaccum problem (either leak, PCV, or EGR). I suspected the original dist cap and rotor were corroded so I remove the old dist cap and rotor (it was corroded and burnt). Reinstalled everything with the new stuff and started it up. Car begins to idle rough but does not stall out as much as it did earlier on (sometimes idle stumbles so much it does stall). Kicking myself for making it worse I decide to check the timing thinking maybe the rotor went back on wrong. Timing was way off (off the chart high). Decided to adjust timing back to 6B as a base. Set it and check it again and the timing moves off the chart again. Seems to be changing itself ...

Next step - So here's where I am now. Either I forgot to disconnect the ESC connector and the ECM was advancing timing, or I have a bad/loose timing chain. I'm going to check it again tomorrow with the ESC connector disconnected to make sure. Does anyone know how to test if the timing chain is bad before taking everything apart? I can see the possibility, all the punishment of the drift session would be hard on that chain, and if its changing timing on the fly that could account for the weird idle/stall issues, as well as the slight pinging or knocking sounds. Does this sound possible to you guys? Bad timing chain causing these weird problems?

Here's a few things on my list:
1. Set the TPS to proper .54 volt output
2. Check and set base timing with ESC connector disconnected
3. Test the ESC connector
4. Check for a vaccum leak w/ guage (never done it before)
5. Check PCV valve with my thumb
6. Check EGR valve by removing vaccum hoses

If I have to do this timing chain I'm gonna use my pete jackson gear drive, replace the water pump, and delete damn EGR.

acescarrsRS

Man it might be the timing chain. Or it could also be a faulty distributor. But both would cause your erratic idle, stumble, stall, etc. problem. Does it backfire too when it idles rough?

CrazyHawaiian

It backfired around the time I had just put in the Barrs Leaks and it first started idling rough and stalling. I was trying to use the throttle to keep it alive and it backfired a few times. It hasn't done any backfiring since I've replaced the TPS and cap/rotor. My neighbors hate me.

acescarrsRS

I'd sure hate for you to go through all the trouble of changing the timing chain & not be the problem! I really don't know anyway to check it though, other than physically pushing on the chain with the cover off. Hope you get this sorted out! I feel your pain.....must be a Camaro thing cause this problem is very similar to mine!

Duck

This is why FI is such a love-hate relationship, sigh. It will often go for years without a whimper, then get horridly bad for no apparent reason.

First thing I'd do is grab an extra distributor, swap it to see if makes a difference. Also, sometimes the distributor spark module gets erratic, I have a spare module for TPI GM distributor and you can have it if you want, since I changed to an MSD distributor a while ago.

I'd also swap in a spare ECM and see if there's a difference.

The problem appears related to open loop/closed loop. I'd unplug/clean/replug everything electronic and check for any broken/burnt/disconnected wiring.

I you do get into the timing chain, it's a good opportunity to upgrade with a two-piece cover.

stew'86MCSS396

Myth...old wives tale??? I've always wanted to venture down that road but have read that knock sensors and gear drives don't like each other. stew

CrazyHawaiian

Thanks for the help guys. I thought about it last night and decided here's what I decided to do next:

Gonna check and set base timing with ESC connector disconnected. If the base timing remains stable and does not fluctuate again then I'm gonna set the TPS to the correct .54 volts and troubleshoot vaccum and IAC. I'm actually hoping the timing will change itself and the chain is bad, its the only thing I've seen so far that could explain the rough idle/stall as well as the slight pinging or knocking.

One thing I dont understand is how it stalls out instantly when I put it into gear. Like as soon as you apply load it dies. I'm trying to figgure out what changes as far as the ECM is concerned when you put it in gear (suddenly advance or retard timing?)

I am also beginning to suspect the ECM itself. It seems that when the car is running and I put it into field service mode with the paperclip something changes right as soon as I insert the paperclip and idle suddenly smooths out and stabalizes at 2,000 RPM with the SES light flashing slow indicating its in closed loop (reading sensors). Then when I pull the clip out the idle goes rough again and drops down to 12,00-1,500RPM like something just changed. Its so strange, I thought field service mode was only supposed to tell you what type of loop its in, but seems like inserting the clip changes the loop mode or something. To make it even weirder, it appears to idle worse in what I'm assuming is open loop (paper clip removed) than it does in closed loop (paper clip inserted) which makes no sense to me.

I heard about that problem with the gear drives too Stew, I'm not sure what to think. I have never tried it before so I dont know if it'll work or not. This Pete Jackson one I have was originally for a different motor project I had a while back using an 89 hydo roller block and heads with a carb intake setup. Its pure luck that it also fits this application and I happen to be in need of the part. I've talked to the guys at Jegs and they told me it should be OK on the 89 L98 with TPI, part is advertised as 87 and up hydro roller exc LT1/LT4 and does not mention anything about knock on the Jegs magazine, but on the Summit magazine for what appears to be the same exact part it does say not recommended for engines with knock sensors. I'm gonna jump into the fire and find out hahaha.

In any event, I wish I had more experience troubleshooting these problems. No Drift Session for me.

transamracer

Here is another easy check you can try. Take the distributor cap off. There are two wires at the base coming from the shaft of the distributor, and these wires go to the module (green and white). Unplu those, carefully, and check the resistance between them. It should read around 850, some people say 850 +/- 50 Ohms, and others 500 to 1500 Ohms. Next test, put one lead on the white wire, and another on the base of the distributor, there should be no reading (in other words, no continuity) thus meanning the pickup coil is not shorted out to the base. This is a common problem that will cause an erratic idle and backfiring. The part is 20bux CDN. Only thing is you have to remove the distributor. I say its worth the test. Liks someone said earlier... I'd hate for you to swap out a timing chain and start the car and have it to the exact same thing.

CrazyHawaiian

Found the problem, it ended up being the IAC motor. Vacuum was within range, timing was good with ESC disconnected, ESC tested good. So in the end I replaced the TPS, IAC, Cap, Rotor, Plugs and cleaned everything up. Car seems to idle smoother than it did before. I haven't been able to hammer it hard yet, still finishing up the rear brakes. I still need to adjust the TPS, been having a problem with my scantool. Looks like I'll be ready for the Sept Driftsession, Juoni, and Driftshowoff events.

acescarrsRS

Glad you got everything all sorted out! Can't wait to see you in action trying out that new wicked suspension setup! Hmmmmm.....now if you could just make it out of your driveway then you'll be fine haha! Gotta raise the car up a little

CrazyHawaiian

Yeah brah I'm itching to get out there. I need to get in some practice before the Driftshowoff. I picked up some more 17's from Rob so looks like I'm gonna have 6 17's and 2 16's for the next event. We went to mount some tires on those new 17's, they are the C5 17x8.5's and we got one tire mounted so far, trash can 225/45/17 Pilot Sports, they look sick. I cant believe the scrape marks on the sidewalk by my house, it was scraping like 6 inches before it even got to the edge LOL